137 Possible mechanisms underlying enhanced intramuscular adipogenesis in Wagyu cattle

Abstract The quality of beef hinges significantly on the abundance of intramuscular fat and tenderness. Intramuscular fat accumulation results directly from intramuscular adipogenesis, while tenderness is adversely affected by collagenous intramuscular connective tissue. Both intramuscular fat and connective tissue originate from fibro/adipogenic progenitors (FAPs), a group of bipotent progenitors. Wagyu cattle are renowned for their tender beef with rich intramuscular fat, likely owing to the distinctive features of Wagyu FAPs. Our study has identified fewer myogenic cells but more FAPs with greater adipogenic potential in Wagyu compared with Angus muscle. Furthermore, single-cell transcriptomic analysis identified that Wagyu FAPs exhibit greater adipogenic and decreased fibrogenic characteristics compared with FAPs in Brahman cattle, which generally produce low-quality beef with limited intramuscular fat and tenderness. Interestingly, Wagyu muscle also contains more abundant vascular cells, crucial for supporting adipogenesis. Mechanistic studies have unveiled several signaling pathways, including the bone morphogenetic protein signaling and the alternative complement pathway of the complement system, which likely contributes to the heightened adipogenic programming of Wagyu FAPs and is subject to epigenetic regulation.